(a) Field of the Invention
The present invention relates to an apparatus and method used to determine angles of inclination and the range of motion of various human joints therefrom, such as, for example, cervical flexion. The apparatus of one preferred embodiment is e computerized arthrometer which is a stand-alone automated apparatus. Output can be provided to a printer for hard copy or to a computer for storage or further manipulation of data. Each sensor or inclinometer used in the preferred embodiment employs a pair of Hall effect transducers spaced about a rotating ring magnet. The voltage output from the transducers can be evaluated to accurately determine the angle of inclination. In another preferred embodiment, instead of the magnet and transducers, the sensors can include circular sensor having six capacitive sectors, each sector changing capacitance as the circular sensor is rotated. The six capacitance values are evaluated to determine the angle of inclination. Another embodiment incorporates the apparatus into readily available "personal computers" ("PCs"). By employing a pair of sensors for selected range of motion tests, measurement accuracy is increased by compensating for the effects of secondary motion, for example, compensating for forward or backward movement of the torso when measuring cervical flexion or cervical extension, respectively.
(b) Description of the Prior Art
There are known single inclinometers which can be determine and display the angle to which they are oriented. It is known to use multiple inclinometers, to position them at different locations on the body, and take readings from the multiple instruments. It is also known to measure an initial starting angle and an ending angle, with the angle therebetween being the range of motion. Further, inclinometers are known which display the angle difference between a first position and a second position.
For example, U.S. Pat. No. 4,912,662, to Butler et al., teaches an inclinometer having a capacitive sensing unit which provides varying capacitance depending upon the orientation of the inclinometer. By comparing the capacitance values to calibrated values stored in look-up tables, the angle of inclination can be determined.
Examples of available inclinometers which can display the difference in motion from a first position to a second position are the Autotilt digital inclinometer from the J-Tech Corporation and the Model SR360 Flexometer from SR Associates.